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    Data Lake Formation:Data preview

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    Data Lake Formation:Data preview

    Last Updated:Jun 29, 2026

    Learn how to preview single-table data and explore data visually or with SQL in the DLF console.

    Use cases

    Data Preview works well when you need to:

    • Get a quick look at the content and distribution of a table.

    • Spot-check whether data meets expectations with sampled previews.

    • View actual field values to verify the table schema.

    • Run simple single-table queries without leaving the console.

    Data Discovery is a better fit when you need to:

    • Filter and preview data through a visual interface.

    • Run cross-table queries and aggregate analysis with custom SQL.

    • Export result sets.

    Note

    Both features use Default Compute Resource and are best suited for quick exploration of small datasets. For large-scale analysis, use dedicated compute engines such as Realtime Compute for Apache Flink, EMR Serverless Spark, or EMR Serverless StarRocks.

    Pricing

    Data Preview and Data Discovery are currently in beta and free to use.

    Prerequisites

    You need SELECT permission on the target table. To grant permissions, see Manage data permissions.

    Data preview

    Procedure

    1. Log on to the DLF console.

    2. In the left-side navigation pane, choose Catalogs. In the catalog tree, navigate to the target Catalog > Database > Table.

    3. On the table details page, click the Data Preview tab.

    4. In the Output Fields section, select the columns to return. Select Select All (*) to include all fields, or pick specific fields to preview.

    5. (Optional) In the Filter Conditions section, add WHERE conditions to filter the data. You can use common comparison operators and logical combinations. If no filter is set, all data is returned.

    6. (Optional) In the Advanced Query section, configure advanced options:

      • Group By: Aggregate results by one or more fields.

      • Order By: Sort results by one or more fields.

      • Limit: Set a maximum number of rows to return.

    7. Click Run to run the query. To start over, click Reset.

    Note

    Queries on large tables may time out due to Default Compute Resource limits. Use Limit and filter conditions to narrow the result set.

    Data discovery

    Procedure

    1. Log on to the DLF console.

    2. In the left-side navigation pane, choose Data Discovery.

    3. Choose an exploration mode:

      • Visual Exploration: Filter and preview data visually without writing SQL. The system generates SQL automatically based on your selections.

      • SQL Discovery: Write and run SQL queries directly. Includes syntax highlighting, validation, and result set export.

    Note

    You can switch between modes at any time from the top of the page.

    Visual query

    1. In the query configuration area, select a Catalog, Database, and Table.

    2. In the Output Fields section, select the columns to return. Select Select All (*) to include all fields, or pick specific fields.

    3. (Optional) In the Filter Conditions section, add WHERE conditions to filter the data.

    4. (Optional) In the Advanced Query section, configure advanced options:

      • Group By: Aggregate results by one or more fields.

      • Order By: Sort results by one or more fields.

      • Limit: Set a maximum number of rows to return.

    5. Click Run to run the query. To start over, click Reset.

    SQL query

    1. In the Query List on the left, click + (New Query) to open a query editor tab.

    2. Select the target catalog and database in the SQL editor.

    3. Write a query. The editor provides syntax highlighting and validation.

      Example:

      SELECT col1, col2, COUNT(*) AS cnt
FROM my_table
WHERE dt = '2024-01-01'
GROUP BY col1, col2
ORDER BY cnt DESC
LIMIT 100;

    4. Click Run to view results.

    5. (Optional) Review past queries in the Query List and export result sets as needed.